The present invention relates to a transparent composition comprising an elastomer and fine particles of fluorine-containing resin, for example, a transparent elastomer composition comprising a fluorine-containing elastomer as a matrix and fine particles of fluorine-containing resin which are finely dispersed in the elastomer. The elastomer composition can provide a molded article having enhanced mechanical strength and is useful as a base elastomer for various molded articles. Further, the elastomer composition can provide an elastomeric molded article which is excellent in mechanical strength and transparency by adding an additive thereto.
It has been known that a fluorine-containing resin is added to a fluorine-containing elastomer. An object of the addition is to enhance mechanical strength by using the fluorine-containing resin as a clean filler and utilizing its friction property thereof. Methods, for mixing the resin and the elastomer, include a dry blend method by using a usual rubber mixing roll, and a method for enhancing dispersibility by using a solvent, and the like.
For example, in JP-A-55-151051, a fluorine-containing rubber excellent in abrasion resistance is obtained by blending a low molecular weight polytetrafluoroethylene (PTFE). Also, JP-A-63-178149 describes a method of adding and mixing a PTFE powder to a fluorine-containing rubber solution to enhance the gas barrier property and mechanical strength of the rubber. Further, JP-A-2-261850 proposes that a fluorine-containing resin is blended in a large amount of from 30 to 150 parts by weight together with an organic solvent to 100 parts by weight of a rubber to lower a friction coefficient and to enhance mechanical properties.
An example of an addition of a fluorine-containing resin to obtain cleanliness is described in WO97/08239. WO97/08239 discloses that a composition prepared by adding 5 to 50 parts by weight of a fluorine-containing resin powder having an average particle size of from 0.2 to 50 xcexcm to 100 parts by weight of a fluorine-containing rubber is excellent as a sealing agent for etching equipment. Also, WO95/02634 discloses that a composition prepared by adding 2 to 50 parts by weight of a fluorine-containing resin fine powder to 100 parts by weight of a rubber component is a clean composition suitable for a wet process of semiconductors.
However, those prior techniques are directed to adding and mixing a fluorine-containing resin to a matrix rubber (elastomer). Although the dispersibility may be enhanced by using a solvent, as a particle size becomes finer, a uniform dispersion is difficult to obtain. For example, when fine particles of a fluorine-containing resin are dispersed in a transparent elastomer, if they are dispersed uniformly, the composition should be transparent. Yet, a transparent elastomer composition in which a fluorine-containing resin is finely uniformly dispersed has not yet been obtained.
If fine particles of a fluorine-containing resin are not dispersed uniformly, a strength of a molded article obtained by vulcanizing and molding is low and the effect of adding the fluorine-containing resin is not obtained sufficiently.
It is therefore an object of the present invention to provide an elastomer composition wherein fluorine-containing resin fine particles are dispersed uniformly in a transparent elastomer, and which can exhibit the maximum effect of adding the fluorine-containing resin.
The present invention relates to a transparent elastomer composition in which fine particles of a fluorine-containing resin are finely dispersed in a transparent elastomer.
It is preferable that the transparent elastomer as a matrix is a fluorine-containing elastomer. Also, it is preferable that the fine particles of a fluorine-containing resin have an average particle size of from 20 to 150 nm.
The present invention also relates to an elastomer composition containing a crosslinking agent and as required, a crosslinking accelerator and a filler.
The elastomer composition of the present invention can be prepared, for example, by mixing an emulsion of transparent elastomer particles and an emulsion of fluorine-containing resin fine particles and then co-coagulating the resulting mixture.
The present invention also relates to an elastomeric molded article obtained by vulcanizing and molding the above-mentioned elastomer composition. The present invention further relates to a transparent elastomeric molded article.
In the present invention, being transparent means that a haze value mentioned hereinbelow is not more than 50%.